A metallic copper thin film (hereinafter simply referred to as “copper thin film”) is employable as a copper circuit of a silicon semiconductor. A metal oxide thin film containing copper oxide (hereinafter simply referred to as “copper oxide thin film”) is expected as material for high-critical temperature superconductors.
As the processes for producing the copper thin film or complex oxide thin film containing copper oxide by vapor deposition procedure, various processes are known. A representative process is a chemical vapor deposition process (CVD process) comprising the steps of thermally decomposing a compound containing a copper atom under specific conditions and depositing the decomposition product on a substrate to produce thereon a copper thin film or a copper oxide thin film.
For the production of a copper thin film or a copper oxide thin film in the CVD process, β-diketonato copper complexes are generally used.
JP-A-5-59551 describes a process for producing a copper thin film (to be used as a copper circuit of a silicon semiconductor) using a β-diketonato copper(I) as a copper source. The β-diketonato copper(I) is advantageously employed because it can be subjected to disproportionation reaction, to deposit metallic copper. However, it has such a defect that the β-diketonato copper (I) is thermally unstable, and that some of β-diketonato copper(I) decompose when these are heated to vaporize in the CVD process.
A typical divalent β-diketonato copper complex employed in the CVD process is dipivaloylmethanato copper(II) complex. This copper complex is more thermally stable than the monovalent β-diketonato copper complex. However, since the dipivaloylmethanato copper(II) complex has such a high melting point as 198° C., it likely deposits in a CVD system and plugs the production line. Other known β-diketonato copper complexes also have the same problem. Moreover, since the dipivaloylmethanato copper(II) complex and other known β-diketonato copper complexes have a low vapor pressure, the thin film production rate is low. Accordingly, these known β-diketonato copper complexes are not appropriate as industrially employable copper sources.
JP-A-2001-181840 describes a β-diketonato copper(II) complex having the following formula (II): which is liquid at room temperature and solves the problems of the known material.
The above-mentioned β-diketonato copper(II) complex exists as a viscous liquid at temperature. Therefore, it is easily supplied in the CVD system and free from the problem of plugging. Nevertheless, it still shows a low film production rate, and therefore, some of the problems in the production workability are still unsolved.